It has been proposed to sense wheel speed and generate wheel speed signals which are then processed to compare the driven speed of the wheels with the speed of the vehicle and, if the wheel speed is in excess of that which it should have to drive the vehicle, a signal is generated which can be used to apply a brake to the wheel which spins or slips or has a tendency to spin or slips or effect other control functions, for example to reduce torque output from the engine to which the wheels are coupled. The referenced literature, German Patent Disclosure Document No. DE-OS 31 27 301 to which British Pat. No. 2,109,882 corresponds, describes a control circuit of this type. If a wheel tends to spin, the associated brake is operated by a brake control system. If two wheels, for example from the same axle, have a tendency to spin, then, additionally, the engine torque can be affected.
Vehicles which have control systems of this type, particularly vehicles which have manual transmissions, may be difficult to start if the surface on which the wheels are located is highly slippery, that is, the coefficient of friction between wheel and road surface is low. The engine may not reach a sufficiently high speed, or may reach the sufficiently high speed not fast enough in order to permit reliable starting of the vehicle on the surface.